Even though the abstract model presented in this paper is versatile in the description of various models, it may be lacking in subtle ways to describe more complex systems. This complexity may be included in one of the components in order to make it fit, though this obscures clear understanding and comparison across models. An example of this is the implicit aggregation in the form of re-ranking as the final step of the DPR question answering system [1]}.
We include it in the core model component, though a better understanding of this model would be achieved by adding an additional aggregator element to the abstract model.
This would, however, conflict with most other systems which would not make use of this and for full description, this part of the pipeline would have to be set to simply identity or NOP. This has happened with other models, as documented in tab:artefactssummary.
